VSTs don't show up in OS X about giada HOT 1 CLOSED

From the VST docs:

In the beginning of VST the Plug-In's GUI was attached at the left-top corner without a mechanism for the host to move it. This and the evolution of the macintosh platform makes it necessary to change this old behaviour. The modern way on Mac OS X to do UI design with C/C++ is to use HIViews and window compositing.
The VST SDK 2.4 requires the Plug-In to attach one HIView to the window and that this HIView can be moved around and that it can be embedded into other subviews.
Hosts which implement VST 2.4 need to provide a window to the Plug-In which is composited if the Plug-In itself uses 2.4. If the Plug-In uses an earlier VST SDK it should provide a non composited window.

Adding an HIView on effEditOpen

As before the ptr in effEditOpen is a WindowRef. You need to add one HIView to the content view of this window.

HIViewRef contentView;
if (HIViewFindByID (HIViewGetRoot ((WindowRef)ptr), kHIViewWindowContentID, &contentView) == noErr)
        HIViewAddSubview (contentView, myPluginView);

Closing on effEditClose

When effEditClose is called you should remove your HIView from the window.

HIViewRemoveFromSuperview (myPluginView);

Don't do anything with the window. It is not your window.

from giada.